Evol Ecol Res 8: 515-527 (2006)     Full PDF if your library subscribes.

Heightened phenotypic variation and age-based fading of ultraviolet butterfly wing coloration

Darrell J. Kemp*

School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA and Department of Zoology, Stockholm University, SE-10691 Stockholm, Sweden

Address all correspondence to Darrell Kemp, School of Tropical Biology, James Cook University, Cairns, QLD 4870, Australia.
e-mail: darrell.kemp@jcu.edu.au

ABSTRACT

Hypothesis: Structural coloration (iridescent ornamentation) should vary more greatly among individuals and with age than pigment coloration. Structural coloration requires nano-scale precision and might thus more honestly signal male age and condition than pigment-based colours.

Organism: A natural population of the orange sulphur butterfly, Colias eurytheme. C. eurytheme females prefer young males, choosing them on the basis of an unknown signal.

Site: Cultivated alfalfa (Medicago sativa) fields near Avondale, Arizona, August–September 2004.

Methods: I randomly sampled 70 ‘pristine’ males and an additional 98 males in five age classes. I then measured key reflectance characteristics (brightness, hue and chroma) of the dorsal structural ultraviolet markings and of the coincident pigmentary yellowish-orange.

Conclusions: Consistent with the sexual selection hypothesis, structural reflectance parameters are more phenotypically variable. Structural reflectance also fades more with age. However, the higher phenotypic variance of structural colour renders it a less precise indicator of male age than pigment colour.

Keywords: age, Colias eurytheme, iridescence, Lepidoptera, mate choice, sexual selection.

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        © 2006 Darrell J. Kemp. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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